Alphabet shares plunge 5% as AI researchers exit

What happened

Alphabet's stock closed down about 5% on Monday after two high-profile exits — Noam Shazeer, vice president of engineering and Gemini AI co-lead, announced he was leaving for OpenAI on Wednesday, and John Jumper, DeepMind vice president and engineering fellow, announced Friday he was joining Anthropic after nine years at the company.

Why it matters

The departures signal concern among investors about whether Alphabet's heavy AI investments — the company has raised $141 billion（約23兆円） in debt and equity since October — will generate lasting returns. Microsoft CEO Satya Nadella said in a Sunday Wall Street Journal interview that the AI market was commoditized and called for less dependence on 'AI Giants,' raising questions about whether lower-cost, interchangeable models could squeeze margins rather than build competitive advantage.

What to watch

Jumper is best known as co-creator of AlphaFold, the AI that has predicted more than 200 million protein structures. The stock decline was the steepest since a roughly 7% drop in May 2025, and users also reported Gmail and YouTube outages on Monday.